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From Nose Cap to Body Flap
Have you ever wondered where the Shuttle orbiter gets its black and white coloring?

Technicians work on insulation tilesThat comes from the black and white tiles, gray reinforced carbon-carbon (RCC) panels and white thermal blankets that make up its Thermal Protection System, which protects the orbiter from the extreme temperatures of launch, space and entry.

In the Orbiter Processing Facility, technicians work on insulation tiles near the landing gear door of orbiter Discovery.

"On each orbiter, there are about 24,000 tiles," said Stilson. "Because every single tile is unique, they are manufactured with a serial number that identifies that tile's size, shape and location on the orbiter."

During a standard flow, about 100 are repaired and replaced. For Discovery's Orbiter Maintenance Down Period (OMDP), that number is up to 1,400 so far -- about twice what was expected.

The orbiter's nose cap and wing leading edges are covered with RCC, providing protection from the 3,000-degree Fahrenheit heat of re-entry. Workers use non-destructive engineering methods, such as CAT scans, to evaluate the RCC panels before installation.

Comparison of bare and painted wing leading edgesWhile the RCC panels are removed, the bare metal of Discovery's wing leading edges are exposed for corrosion repair. When every inch and rivet of the leading edge has been inspected and repaired, two coats of an anticorrosive compound and one coat of gleaming white paint are evenly applied with a spray gun.

The orbiter's airframe, including the wing leading edges, are made of high-grade aluminum. In the image at left, the wing leading edge has been stripped bare for inspection. The image at right shows the wing leading edge after anticorrosive compound and paint are applied.

A "first" is happening beyond Discovery's wings. For the first time in Shuttle history, work is underway to remove the parts that drive the rudder speed brake's movement. Located in the back of the tail, the rudder speed brake comprises four panels that open outward during landing, creating drag and slowing the vehicle. Four unique rotary mechanisms, called actuators, control the RSB panels, and workers are carefully lifting them onto twin scales joined together, in order to determine the actuators' center of gravity.

"Because Discovery's main engine compartment is so crowded with hardware, workers have to get into some pretty creative positions to open and inspect bundles of wires encased in protective black tubing," Scott said. The lines that feed Discovery's three main engines are color-coded to indicate whether they carry gaseous or liquid hydrogen or oxygen.

Workers install a new liquid oxygen feedlineDuring standard Orbiter Major Modification inspections, technicians found a crack in a metal ball that is part of a 17-inch pipeline that delivers liquid oxygen to the Space Shuttle Main Engines. The finding led to a fleet-wide inspection, ensuring no other cracks existed. Later, a new 17-inch line was installed in Discovery -- work that was never expected to be required and had never been done before. Several NASA Centers contributed Shuttle expertise to resolve the problem successfully.

Workers in the Orbiter Processing Facility insert the liquid oxygen feedline for the 17-inch disconnect in the orbiter Discovery.

During re-entry, Discovery's main engines are partially protected by the body flap, which also helps control the up-and-down motion of the orbiter. Because the aft end of the orbiter is a very corrosive environment during launch, the body flap also endured a thorough structural inspection before it was repainted.

From nose cap to body flap, Shuttle Discovery's overhaul is no small task. But the amount of care and attention to detail required during OMDP ensures that when the Shuttle fleet returns to safe flight, Discovery will be healthy and ready to take on her next assignment.

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+ Part 1: My Shuttle's in the Shop
+ Part 2: Into the Orbiter
Anna Heiney
NASA's John F. Kennedy Space Center